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Solar System Moons Series

Europa

An ocean under the ice: the most promising place to search for life in the solar system.

Author: Juan Carlos Euyoque Aguilera · October 7, 2026 · CC BY 4.0

Image of Europa (NASA/JPL, public domain)
Europa (Galileo spacecraft, NASA/JPL, public domain). Not to scale.
3,121.6 km
Diameter
671,000 km
Distance from Jupiter
3.551 days
Orbital period
~100 K
Temperature

Europa orbits Jupiter at 671,000 km, wrapped in a water-ice crust crossed by reddish lines. Beneath it —magnetic measurements from Galileo indicate— there may be a global ocean of liquid water holding perhaps twice the water of all Earth's oceans.

Tidal heating keeps that ocean liquid despite the cold outside (~100 K at the surface). NASA's Europa Clipper mission, already en route, will study whether that ocean could be habitable.

Measured data [DATO]

DataValueStatusSource
Diameter3,121.6 km[DATO] observadoNASA Planetary Fact Sheets
Mass4.80×10²² kg[DATO] observadoNASA Planetary Fact Sheets
Mean density3,010 kg/m³[DATO] observadoNASA Planetary Fact Sheets
Surface gravity1.315 m/s²[DATO] observadoNASA Planetary Fact Sheets
Orbital period3.551 days[DATO] observadoNASA Planetary Fact Sheets
Rotation periodsynchronous (3.551 days)[DATO] observadoNASA Planetary Fact Sheets
Distance from Jupiter671,000 km[DATO] observadoNASA Planetary Fact Sheets
Temperature~100 K at the surface[DATO] observadoNASA Science
AtmosphereTenuous: molecular oxygen[DATO] observadoNASA Science
Notable featureEvidence of a subsurface global ocean (Galileo magnetometer)[DATO] observadoNASA Science

Truths [DATO]

  • [DATO] Galileo's magnetometer detected an induced magnetic field at Europa: the strongest explanation is a global salty-water ocean under the ice, responding to Jupiter's field.
  • [DATO] The reddish 'lineae' are ice fractures stained by salts: the crust cracks and renews itself — ice tectonics.
  • [DATO] The Hubble telescope observed possible water-vapor plumes venting from Europa's south pole.
  • [DATO] Europa endures intense radiation from Jupiter: its surface is one of the most radioactive environments in the solar system — the ocean, under kilometers of ice, would be shielded.

Labeled myths [MITO]

[MITO] Life has already been found on Europa.

False: there is strong evidence of an ocean, but no life has been detected. Europa Clipper will investigate habitability (the ingredients), not life directly.

Fuente: NASA Science

[MITO] Europa's ice is thin and easy to drill through.

False: the crust's estimated thickness is ~15–25 km from models — estimated, not measured — and drilling it is beyond any current technology.

Fuente: NASA Science

Open questions [PREGUNTA]

  • [PREGUNTA] How thick really is the ice crust?
  • [PREGUNTA] Are there active plumes today that a probe could sample?
  • [PREGUNTA] Does the ocean have the chemistry life needs?

The chain in brief

  1. [DATA] 1. Ice over a possible ocean: It orbits Jupiter at 671,000 km, wrapped in a water-ice crust crossed by reddish lines, with ~100 K at the surface.
  2. [MODEL] 2. The ocean the magnetometer points to: Galileo detected an induced magnetic field at Europa: the strongest explanation is a global ocean of salty water under the ice, which could hold twice the water of all Earth's oceans.
  3. [DATA] 3. A crust that cracks and renews itself: The reddish 'lineae' are ice fractures stained by salts — ice tectonics; Hubble also observed possible water-vapor plumes at its south pole.
  4. [DATA] 4. Radiation outside, shelter inside: Europa endures intense radiation from Jupiter and its surface is one of the most radioactive environments in the solar system; the ocean, under kilometers of ice, would be shielded.
  5. [DISPUTED] 5. What Clipper is coming to check: How thick the ice crust really is, whether plumes are active today, and whether the ocean has the chemistry life needs remain open; NASA's Europa Clipper mission is already en route.